U.S. patent number 10,816,643 [Application Number 15/917,070] was granted by the patent office on 2020-10-27 for temperature sensor system, radar device and method.
This patent grant is currently assigned to NXP B.V.. The grantee listed for this patent is NXP B.V.. Invention is credited to Matthis Bouchayer, Dominique Delbecq, Cristian Pavao Moreira, Pierre Savary.
United States Patent |
10,816,643 |
Bouchayer , et al. |
October 27, 2020 |
Temperature sensor system, radar device and method
Abstract
A radar device (100) is described that includes at least one
transceiver (205) configured to support frequency modulated
continuous wave (FMCW); a digital controller (262); and a
temperature sensor system comprising a plurality of temperature
sensors (222, 232, 242) coupled to various circuits (220, 230, 240)
in the at least one transceiver (205). The digital controller (262)
of the radar device (100) is configured to monitor a temperature of
the various circuits (220, 230, 240) by polling temperature values
of the plurality of temperature sensors (222, 232, 242).
Inventors: |
Bouchayer; Matthis (Toulouse,
FR), Pavao Moreira; Cristian (Frouzins,
FR), Delbecq; Dominique (Fonsorbes, FR),
Savary; Pierre (Muret, FR) |
Applicant: |
Name |
City |
State |
Country |
Type |
NXP B.V. |
Eindhoven |
N/A |
NL |
|
|
Assignee: |
NXP B.V. (Eindhoven,
NL)
|
Family
ID: |
1000005142254 |
Appl.
No.: |
15/917,070 |
Filed: |
March 9, 2018 |
Prior Publication Data
|
|
|
|
Document
Identifier |
Publication Date |
|
US 20180292511 A1 |
Oct 11, 2018 |
|
Foreign Application Priority Data
|
|
|
|
|
Apr 11, 2017 [EP] |
|
|
17305433 |
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G01K
1/026 (20130101); G01S 7/4017 (20130101); G01S
13/34 (20130101); G01S 13/86 (20130101); G01S
7/4021 (20130101); G01S 7/4004 (20130101); G01S
7/4008 (20130101); G01S 7/4056 (20130101); G01S
2007/4013 (20130101) |
Current International
Class: |
G01S
7/40 (20060101); G01K 1/02 (20060101); G01S
13/86 (20060101); G01S 13/34 (20060101) |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Diallo; Mamadou L
Attorney, Agent or Firm: Jacobsen; Charlene R.
Claims
The invention claimed is:
1. A radar device comprises: at least one transceiver configured to
support frequency modulated (FM) radar signals; a digital
controller; and a temperature sensor system comprising a plurality
of temperature sensors coupled to various circuits in the at least
one transceiver; wherein the digital controller is configured to
monitor a temperature of the various circuits by polling
temperature values of the plurality of temperature sensors, and
wherein the frequency modulated radar signals are frequency
modulated continuous wave, FMCW, signals and the digital controller
is configured to stop the polling of sensor temperature values when
a FMCW ramp process is started and re-start the polling of sensor
temperature values following a completion of an FMCW signal
generation and reception process and the radar device switching to
an IDLE mode of operation.
2. The radar device of claim 1 wherein the digital controller is
configured to read a plurality of temperature values of the
plurality of temperature sensors and compare at least one read
temperature value with at least one temperature threshold value,
and in response to the comparison exceeding a threshold, the
digital controller initiates a shutdown operation.
3. The radar device of claim 1 wherein the temperature sensor
system further comprises a single analog to digital converter, ADC,
operably coupled to a register and configured to convert a polled
analog temperature value of one of the plurality of temperature
sensors to a digital format and store the digital representation of
the temperature value in the register.
4. A radar device comprises: at least one transceiver configured to
support frequency modulated (FM) radar signals; a digital
controller; and a temperature sensor system comprising a plurality
of temperature sensors coupled to various circuits in the at least
one transceiver; wherein the digital controller is configured to
monitor a temperature of the various circuits by polling
temperature values of the plurality of temperature sensors, and
wherein the digital controller is configured to read a plurality of
temperature values of the plurality of temperature sensors and
compare at least one read temperature value with at least one
temperature threshold value, and in response to the comparison
exceeding a threshold, the digital controller initiates a shutdown
operation.
5. The radar device of claim 4, wherein the temperature sensor
system further comprises a single buffer operably coupled to the
multiplexer and configured to provide a gain and DC level
adjustment to a single output from the multiplexer across each
temperature value.
6. The radar device of claim 4, wherein the temperature sensor
system further comprises a multiplexer operably coupled to the
digital controller and configured to select a single temperature
value from the plurality of temperature sensors in a polling
operation.
7. The radar device claim 4 wherein the digital controller is
configured to monitor at least one temperature of the plurality of
temperature sensors in both an analog domain and a digital
domain.
8. The radar device of claim 4 wherein the temperature sensor
system further comprises a single analog to digital converter, ADC,
operably coupled to a register and configured to convert a polled
analog temperature value of one of the plurality of temperature
sensors to a digital format and store the digital representation of
the temperature value in the register.
9. A radar device comprises: at least one transceiver configured to
support frequency modulated (FM) radar signals; a digital
controller; and a temperature sensor system comprising a plurality
of temperature sensors coupled to various circuits in the at least
one transceiver; wherein the digital controller is configured to
monitor a temperature of the various circuits by polling
temperature values of the plurality of temperature sensors, and
wherein the temperature sensor system further comprises a
multiplexer operably coupled to the digital controller and
configured to select a single temperature value from the plurality
of temperature sensors in a polling operation.
10. A radar device comprises: at least one transceiver configured
to support frequency modulated (FM) radar signals; a digital
controller; and a temperature sensor system comprising a plurality
of temperature sensors coupled to various circuits in the at least
one transceiver; wherein the digital controller is configured to
monitor a temperature of the various circuits by polling
temperature values of the plurality of temperature sensors, and
wherein the digital controller is configured to monitor at least
one temperature of the plurality of temperature sensors in both an
analog domain and a digital domain.
11. The radar device of claim 10 wherein the digital controller is
configured to monitor a temperature in an IDLE mode of operation,
where a selected temperature value is stored and read using a
serial peripheral interface, SPI, clock.
12. The radar device of claim 10 wherein the temperature sensor
system further comprises a switch configurable to provide an analog
temperature measurement value to an output pin when the radar
device is switched to an IDLE mode of operation from a FM mode of
operation.
13. The radar device of claim 12 wherein the digital controller
selects which temperature sensor measurement to provide to the
output pin upon the radar device switching to an IDLE mode of
operation.
14. A radar device comprises: at least one transceiver configured
to support frequency modulated (FM) radar signals; a digital
controller; a temperature sensor system comprising a plurality of
temperature sensors coupled to various circuits in the at least one
transceiver, wherein the digital controller is configured to
monitor a temperature of the various circuits by polling
temperature values of the plurality of temperature sensors; and a
single analog to digital converter, ADC, operably coupled to a
register and configured to convert a polled analog temperature
value of one of the plurality of temperature sensors to a digital
format and store the digital representation of the temperature
value in the register.
15. The radar device of claim 14 wherein the single ADC supports
analog to digital conversion of a plurality of temperature sensor
values over at least two different ranges, whereby a first
temperature range is configured to provide more resolution than a
second temperature range in order to improve accuracy at the hot
temperatures.
16. A method for supporting frequency modulated (FM) radar signals,
wherein the frequency modulated radar signals are frequency
modulated continuous wave (FMCW) signals, the method comprising:
monitoring a temperature of various circuits in at least one
transceiver of a radar device, wherein the at least one transceiver
is configured to support the frequency modulated radar signals;
receiving a plurality of temperature measurements from a plurality
of temperature sensors coupled to the various circuits; polling
temperature values of the plurality of temperature sensors;
stopping the polling of sensor temperature values when a FMCW ramp
process is started; and re-starting the polling of sensor
temperature values following a completion of an FMCW signal
generation and reception process.
17. A method for supporting frequency modulated (FM) radar signals,
the method comprising: monitoring a temperature of various circuits
in at least one transceiver of a radar device, wherein the at least
one transceiver is configured to support the frequency modulated
(FM) radar signals; receiving a plurality of temperature
measurements from a plurality of temperature sensors coupled to the
various circuits; polling temperature values of the plurality of
temperature sensors; and selecting one of a plurality of stored
temperature values as being a representative temperature.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
This application claims the priority under 35 U.S.C. .sctn. 119 of
European Patent application no. 17305433.9, filed on 11 Apr. 2017,
the contents of which are incorporated by reference herein.
FIELD OF THE INVENTION
The field of the invention relates to a temperature sensor system
for a frequency modulated (FM), such as a FM continuous wave (FMCW)
radar device, and a method therefor.
BACKGROUND OF THE INVENTION
Automotive Radar systems often consist of a multi-chip solution,
combining a radar transceiver (TRx) integrated circuit (IC) and a
microcontroller unit (MCU) IC. As safety is a main concern for such
automotive radar systems, several types of sensors are also
integrated in such multi-chip solutions to ensure that the radar
device is functioning in safe operating conditions. In such
applications, temperature sensors and related temperature sensor
systems are of particular importance, since they can detect if the
device is operating within a safe temperature range.
In a radar device transceiver, it is important to accurately sense
the temperature independently of the radar device state. Two
modes/states of operation for temperature sensing are employed: an
IDLE state where no internal clock is available and all other
functional states where an internal clock is available. The way
that the temperature system is managed and monitored in each mode
is, thus, different. A typical temperature sensor system includes
both analog and digital parts (often separate integrated circuits)
in order to provide good accuracy and programmability. Radar
systems have specified an over-temperature shutdown operation with
programmable thresholds for a majority of the radar device's
functional states. The temperature tracking and over-temperature
shutdown is typically viewed as a four step process, including:
sensing, converting, digitizing, and reading. If an
over-temperature is detected, a shutdown is proceeded to cool down
the chip. When several sensors are used, particularly temperature
sensors, the inventors of the present invention have recognized and
appreciated that the temperature sensor system in an FMCW radar
device, and particularly when switching between sensors, may
disturb the frequency-modulated continuous wave (FMCW) modulation
waveforms transmitted and received by the radar device. Such
temperature sensor disturbances create glitches in the FMCW
modulated signal and disturb the FMCW chirp linearity, thereby
compromising the radar performance and target detection.
US 2015/0241553 A1 describes a radar data processing system that
employs several sensors, including one or more temperature sensors
used for monitoring the temperature. It ensures that the
transmitter is operating within the approved operating
conditions.
U.S. Pat. No. 8,970,234 B2 describes a threshold-based
temperature-dependent power/thermal management concept with
temperature sensor calibration. Temperature readings from a
temperature sensor are measured and reported to a power management
unit. This unit may be configured to periodically compare
temperature readings from the temperature sensing units and may
perform control actions to ensure that an IC is within the
designated thermal limits, to avoid heat related damage.
Accordingly, it is important to provide temperature sensing whilst
generating or processing modulation signals for FMCW radar devices,
without creating glitches in the FMCW modulated signal and
disturbing the FMCW chirp linearity.
SUMMARY OF THE INVENTION
The present invention provides a FM radar device, a temperature
sensing system for such a FM radar device, and a method therefor as
described in the accompanying claims. Specific embodiments of the
invention are set forth in the dependent claims. These and other
aspects of the invention will be apparent from and elucidated with
reference to the embodiments described hereinafter.
BRIEF DESCRIPTION OF THE DRAWINGS
Further details, aspects and embodiments of the invention will be
described, by way of example only, with reference to the drawings.
In the drawings, like reference numbers are used to identify like
or functionally similar elements. Elements in the figures are
illustrated for simplicity and clarity and have not necessarily
been drawn to scale.
FIG. 1 illustrates a simplified block diagram of a radar device,
adapted in accordance with examples of the invention.
FIG. 2 illustrates a high-level temperature sensor example block
diagram of a radar device, in accordance with examples of the
invention.
FIG. 3 illustrates a simplified flowchart of a temperature sensor
system, in accordance with examples of the invention.
FIG. 4 illustrates a temperature sensor example block diagram of a
radar device, in accordance with examples of the invention.
FIG. 5 illustrates an example flow diagram of a radar device, for
example for the temperature sensor example block diagram of FIG. 4,
in accordance with examples of the invention.
FIG. 6 illustrates an example of an IDLE state temperature
measurement, in accordance with examples of the invention.
FIG. 7 illustrates an example of a timing diagram in an MILE state
temperature measurement, in accordance with examples of the
invention.
FIG. 8 illustrates an example of a Functional state temperature
measurement, in accordance with examples of the invention.
FIG. 9 illustrates an example of a timing diagram in a Functional
state temperature measurement, in accordance with examples of the
invention.
FIG. 10 illustrates a simplified flowchart of an over-temperature
shutdown, in accordance with examples of the invention.
FIG. 11 illustrates an example of a timing diagram in a Functional
state temperature measurement during an over-temperature shutdown,
in accordance with examples of the invention.
DETAILED DESCRIPTION
In accordance with some example embodiments of the present
invention, there is provided a FM, or more particularly a FMCW,
radar unit that has multiple temperature sensors that are monitored
by polling. In particular, when switching to an IDLE mode of
operation from a FMCW mode of operation, one temperature sensor is
selected and the sensor polling operation is halted. In this
manner, timing glitches when switching between sensors,
particularly in an FMCW radar device, may be substantially
avoided.
Although examples of the invention are described with respect to
FMCW radar systems, it is envisaged that examples of the invention
may be used with any kind of frequency modulation (FM) technique
(FM, FMCW, FMCW-frequency shift keyed (FSK)) that is sensitive to
glitches. The described temperature sensor system, having several
sensors and common circuitry to reduce die area, may be used in any
type of temperature-sensitive, sensor-based device. In order to
read values of all sensors used, a polling method is proposed.
Furthermore, the polling technique described herein may be extended
to any system or device that employs temperature sensors where it
is advantageous to avoid continuously monitoring sensor values.
Examples of the invention describe a radar device that includes at
least one transceiver configured to support frequency modulated
continuous wave (FMCW); a digital controller; and a temperature
sensor system comprising a plurality of temperature sensors coupled
to various circuits in the at least one transceiver. The digital
controller is configured to monitor a temperature of the various
circuits by polling temperature values of the plurality of
temperature sensors. The concept of `polling` in examples of the
invention encompasses a process where a controller consecutively
triggers or accesses one (or more) from a plurality of sensor
measurements, and particularly a temperature sensor value. In this
manner, multiple temperature sensors and multiple concurrent sensor
measurements can be monitored using a single processing pipeline
whereby each of the plurality of measured temperature values is
individually and repetitively polled.
In some examples, the temperature sensor system may include a
multiplexer operably coupled to the digital controller and
configured to select a single temperature value from the plurality
of temperature sensors in a polling operation. In some examples,
the temperature sensor system may include a single buffer operably
coupled to the multiplexer and configured to provide a gain and DC
level adjustment to a single output from the multiplexer across
each temperature value. In some examples, the digital controller
may be configured to monitor at least one temperature of the
plurality of temperature sensors in both an analog domain and a
digital domain.
In some examples, the digital controller may be configured to halt
the polling operation of the plurality of temperature sensors upon
the digital controller determining that the radar device is
switched to an IDLE mode of operation from a FMCW mode of
operation. In some examples, the digital controller may be
configured to monitor a temperature in an IDLE mode of operation,
where a selected temperature value is stored and read using a
serial peripheral interface, SPI, clock. In some examples, the
temperature sensor system may include a switch configurable to
provide an analog temperature measurement value to an output pin
when the radar device is switched to an IDLE mode of operation from
a FMCW mode of operation. In some examples, the digital controller
may select which temperature sensor measurement to provide to the
output pin upon the radar device switching to an IDLE mode of
operation.
In some examples, the temperature sensor system may include a
single analog to digital converter, ADC, operably coupled to a
register and configured to convert a polled analog temperature
value of one of the plurality of temperature sensors to a digital
format and store the digital representation of the temperature
value in the register. In some examples, the single ADC may support
analog to digital conversion of a plurality of temperature sensor
values over at least two different ranges, whereby a first
temperature range is configured to provide more resolution than a
second temperature range in order to improve accuracy at the hot
temperatures (e.g. In the first temperature range). In this manner,
an accurate and flexible temperature sensor system in a radar
transceiver is provided that includes temperature tracking and
over-temperature shutdowns.
In examples of the invention, several sensors enable the
temperature at different location of the chip to be known, with the
possibility to read the information both in analog and digital
form. A mechanism to support a digital reading of a temperature
(from multiple temperature sensors) is beneficial to storing an
image of the temperature in a register or memory. Additionally, in
some examples, a provision of an analog voltage (termed `SENSE`
hereafter) of the raw (analog) information concerning the
temperature may be advantageously measured and monitored
independently from the digital code. This provides a useful back-up
assessment of the device's temperature, for example should one or
more of the following occur: the register is corrupted, the SPI
connection is broken or busy, or if the Sensor ADC has developed a
problem.
Referring now to FIG. 1, a simplified block diagram of a radar
device 100 operating at millimeter (MMW) frequencies is
illustrated, in accordance with examples of the invention. The
radar device 100 contains one or several antennas 102 for receiving
radar signals 121, and one or several antennas 103 for transmitting
radar signals 121, with one respective antenna shown for each for
simplicity reasons only. The number of antennas 102, 103 used may
depend on the number of radar receiver and transmitter channels
that are implemented in a Oven radar device. One or more receiver
chains, as known in the art, include receiver front-end circuitry
106, effectively providing reception, frequency conversion,
filtering and intermediate or base-band amplification, and finally
an analog-to-digital conversion. In some examples, a number of such
circuits or components may reside in signal processing module 108,
dependent upon the specific selected architecture. The receiver
front-end circuitry 106 is coupled to the signal processing module
108 (generally realized by a digital signal processor (DSP)). A
skilled artisan will appreciate that the level of integration of
receiver circuits or components may be, in some instances,
implementation-dependent.
A controller 114, for example in a form of a microcontroller unit
(MCU), maintains overall operational control of the radar device
100, and in some examples may comprise time-based digital functions
(not shown) to control the timing of operations (e.g. transmission
or reception of time-dependent signals, FMCW modulation generation,
etc.) within the radar device 100. The controller 114 is also
coupled to the receiver front-end circuitry 106 and the signal
processing module 108. In some examples, the controller 114 is also
coupled to a memory device 116 that selectively stores operating
regimes, such as decoding/encoding functions, and the like.
As regards the transmit chain, this essentially comprises a power
amplifier (PA) 124 coupled to the transmitter's one or several
antennas 103, antenna array, or plurality of antennas. In radar
device 100, radar transceiver topology is different from
traditional wireless communication architectures (e.g.
Bluetooth.TM. WiFi.TM. etc.), as modulation occurs within a phase
locked loop (PLL) (typically via a fractional-N divider), and is
applied directly to the PA 124. Therefore, in some examples, the
receiver front-end circuitry 106 and transmitter PA 124 are coupled
to frequency generation circuit 130 arranged to provide local
oscillator signals. The generated local oscillator signals are thus
modulated directly to generate transmit radar signals, and also
used to down-convert received modulated radar signals to a final
intermediate or baseband frequency or digital signal for processing
in a receive operation.
In accordance with examples of the invention, at least one
transceiver of the radar device 100, for example including at least
one transceiver, is configured to support frequency modulated
continuous wave (FMCW). A temperature sensor system 118 includes a
plurality of temperature sensors coupled to various circuits in the
at least one transceiver. The digital controller 114 is configured
to monitor a temperature of the various circuits by polling
temperature values of the plurality of temperature sensors, as
described with reference to, inter alia, FIG. 2.
In FIG. 1, a single signal processor 108 or single microcontroller
unit (MCU) 114 may be used to implement a processing of received
radar signals. Clearly, the various components within the radar
device 100 can be realized in discrete or integrated component
form, with an ultimate structure therefore being an
application-specific or design selection. A skilled artisan will
appreciate that the level of integration of circuits or components
may be, in some instances, implementation-dependent.
Referring now to FIG. 2, a high-level temperature sensor example
block diagram of a radar device 200 is illustrated in accordance
with examples of the invention. The radar device 200 is composed of
a radar transceiver 205 that includes a power management function
210, which may be in a form of a power management IC, and one or
more receivers 220, frequency synthesizers 230, transmitters 240.
Each of the one or more receivers 220, frequency synthesizers 230,
transmitters 240, may include one or more respective temperature
sensors 222, 232, 242 coupled to a temperature sensor system 270.
The radar transceiver 205 also includes a digital part, which may
be in a form of a digital IC 260, which includes a digital
controller 262, such as MCU 114 from FIG. 1 operably coupled 261 to
a storage device 264, such as registers and/or memory. The power
management function 210 generates reference currents and voltages
that are needed within radar device 200.
The frequency synthesizers 230 include all the function related to
generation of the reference frequencies. The transmitters 240
contain the functionality related to the emitted signal, whilst the
receivers 220 are dedicated to the reception and conversion of the
reflected received radar signal. Amongst all the sensors
implemented (with only a few potential sensors illustrated in FIG.
2 for simplicity purposes only), the temperature sensor system 270
is configured to sense an operating temperature at different
locations of the radar transceiver 205. In this example, the
digital controller 262 takes the values from the temperature sensor
system via bus 272. These values are stored in the registers of the
storage unit 264. These values can also be read by the user via the
serial peripheral interfaces (SPIs) 280, and SPI 258 associated
with the MCU 250, via bus 265. The digital controller 262 of the
radar transceiver 205 is also directly connected to SPI 280. The
MCU 250 includes a processing unit 252, a storage unit 254, a
digital controller 256 and SPI 258 to communicate with the radar
transceiver 205.
The stored values may also be compared to programmable thresholds
(not shown). If a stored value is, say, higher than a threshold it
may indicate that there is an over-temperature on the IC. In this
instance, a flag is generated by the digital controller 262 and the
fault condition stored in a fault register via path 263. As the IC
should operate in safe conditions, a shutdown may be proceeded with
in this situation.
In a shutdown situation, the digital controller 262 sends the ICs
into a power-save mode in order to cool down the chip. In a typical
example, receivers 222 and transmitters 242 are powered down,
whilst frequency synthesizers 232 and power management function 210
are placed into a low power mode via control signals sent on path
269. Also, in some examples, a flag 285 (from a number of potential
flags 281), may be sent from the digital controller 262 to the
interrupt (INT) pin 286 via an `OR` logic gate 282 to indicate
externally that an interrupt event has happened. The analog value
from the temperature sensor system can then also be routed and
measured on a SENSE pin 288 through, say, a multiplexer 284.
In accordance with examples of the invention, the radar device
includes at least one transceiver 205 configured to support
frequency modulated (FM) radar signals, such as FMCW radar signals,
and digital controller 262. Temperature sensor system that includes
a plurality of temperature sensors 222, 232, 242 coupled to various
circuits such as transmitter 240, receiver 220, frequency
generation circuit 230. The digital controller 262 is configured to
monitor a temperature of the various circuits by polling
temperature values of the plurality of temperature sensors 222,
232, 242. In some examples, the digital controller 262 may be
configured to stop the polling of sensor temperature values when a
FMCW ramp process is started; and re-start the polling of sensor
temperature values following a completion of an FMCW signal
generation and reception process. In some examples, the multiplexer
284 under control of the digital controller 262 may be configured
to select a single temperature value from the plurality of
temperature sensors 222, 232, 242 in a polling operation.
The MCU 250 includes a processing unit 252, a storage unit 254, a
digital controller 256 and SPI 258 in order to communicate with the
radar transceiver 205. The processing unit 252 is responsible for
the digital signal processing of the data received from the radar
transceiver 200, this data being, say, representative of a radar
target speed, distance or speed variation. The storage unit 254 is
the general memory of the MCU 250 that is responsible for both
dynamic data storage (random access memory (RAM) and/or flash
memory) as well as read only memory (ROM) (static) data storage.
The digital controller 256 is in charge of the communication
between all MCU different blocks and units, together with
sequencing all the process (state machine) for the correct
operation of the MCU 250.
Referring now to FIG. 3, a temperature sensor flowchart 300 is
presented, according to the different operational states supported
by the radar device, such as radar device 100 of FIG. 1. In this
example, prior to a first use, a trim flow operation in 302 is
performed for the radar transceiver IC. A skilled person will
appreciate that trimming may be performed as there are two types of
variations that any IC may be subjected to that could affect its
performance (or affect the performance uniformity across multiple
same IC): process and mismatch variations. Therefore, in order to
reduce the impact on the temperature transfer function of such
process and mismatch variations between ICs, a trimming flow
selects the best value of the relevant parameters that compensates
for such variations, prior to first use. In this manner, the
accuracy of the performance of the temperature sensors across
multiple ICs and batches may be better guaranteed/matched.
After the trim flow operation in 302, the radar system is ready at
304), which means that the temperature sensor system is fully ready
to operate. In this example of a temperature sensor flowchart 300,
two modes are differentiated. The first mode of operation 306 is a
radar device in an IDLE state 308, where there is no internal clock
available 310. Thus, an SPI clock is required for the temperature
tracking, storage and reading of the values in 312. The IDLE state
is the safest in terms of functionality and the lowest in terms of
power consumption, which means that there is no need of an
over-temperature shutdown in this particular state.
In the second mode of operation 314, the various operations of the
radar device are grouped into all the remaining functional states
of the radar system in 316. Temperature tracking is also performed
in this mode at 320. The main difference with the first IDLE mode
is that an internal clock is available, and thus the temperature
sensed values are polled and periodically stored. Furthermore, the
stored temperature sensed values can also still be read via the
SPI. The over-temperature shutdown operation is required and
automatically checked at 320 too.
Referring now to FIG. 4, a temperature sensor example block diagram
400 of a radar device is illustrated, in accordance with examples
of the invention. As illustrated, the temperature sensor example
block diagram 400 includes, inter alia, four primary operational
circuits/units: a sensing unit 270, a converting unit 450, a
digitizing unit 260 and a reading unit 440. Ideally, a temperature
sensor system has to deal with the following trade-offs: provide
high accuracy (for both temperature tracking and programmable
over-temperature shutdown), support in both analog and digital
circuits in order to read the sensed temperature, limit the area
taken on the chip to implement temperature sensing, as well as have
low current consumption in order to avoid self-heating and power
dissipation.
In some examples, the sensing unit 270 is composed of two stages: a
first stage includes a number of, for example, two-diode based
sensors 422, 424, 426, although other sensors can be used. A
differential signal is amplified and converted to a single-ended
signal. This first stage is shared between each temperature sensor
(T_SENS1 . . . T_SENS3) 422, 424, 426. A multiplexer 284 is
configured to select one signal (or value) from the first stage in
a polling operation between multiple selectable temperature signals
(or values), based on a temperature sensor select control signal
474 and provides a single V.sub.single signal to a second stage,
which in this example is a buffer 470. This second (buffer 470)
stage is advantageously common for all the temperature sensors, in
order to save area and reduce current consumption. In this example,
the second buffer 470 stage performs both amplification and DC
level adjustment. A V.sub.sense signal 471 output from the second
buffer 470 stage is input to a sensor analog-to-digital converter
(ADC) 490 in order to convert the analog data into a digital form.
In some examples, a Flash-like ADC may be used, for example with
two different ranges, whereby one range is configured to provide
more resolution than the other range in order to improve accuracy
at the hot temperatures.
In this manner, multiple temperatures are measured at different
locations of the chip where a useful and significant portion of
circuitry may be shared across all temperature sensors, e.g. the
buffer 470 and sensor ADC 490, with just one temperature
measurement being selected. In this example, the sensor ADC 490 is
a single input ADC to limit the chip area used. A Flash-like
structure for the ADC is chosen to be able to perform the
analog-digital conversion even without a clock, in order to
facilitate temperature measurements being monitored even in an IDLE
state. Thus, in this example and even when there should be minimal
heat generated in an IDLE state, it is possible to monitor
potential problems, such as the circuit being again re-started with
a still too-high temperature after an over-temp shutdown. The
sensor ADC 490 uses a reference voltage V.sub.ref, for example
provided by a regulator in the power management unit 210. In some
examples, at the output of the sensor ADC 490, a thermometric code
is used to transfer the data into a digital form. The digitizing
unit 260 performs a number of different operations. Firstly, the
thermometric code is converted into a binary code, equivalent to,
say, 6.5 bits in this example. As the flash-like sensor ADC 490
has, in some examples, two ranges with different resolutions, the
slope of the code (in temperature) may not be linear. A
linearization may thus be performed, providing, say, a code with 8
bits. This 8-bit digital value is then stored into a register, such
as storage device 264 of FIG. 2. The reading unit 440 is configured
to read an image of the temperature, which is advantageously
possible to be read in analog form, by routing the V.sub.sense
signal 471 on a pin (SENSE pin) 473, as well as the digital stored
value being readable in digital form.
Referring now to FIG. 5, an example trimming flow diagram 500 for a
temperature sensor of a radar device, for example for the
temperature sensor example block diagram of FIG. 4, is illustrated
in accordance with examples of the invention. First, a regulator
providing the reference voltage V.sub.ref is trimmed in 505. The
goal of trimming V.sub.ref is to obtain a low spread on this
voltage used by the ADC, such as sensor ADC 490 of FIG. 4. Then,
the ADC is characterized through testing, in order to determine
precisely its input range in 510, defined by its minimum input
voltage V.sub.bottom and its maximum input voltage V.sub.rep. In
this example, the current injected in the diodes of the T_SENS are
then trimmed in 515, in order to adjust a slope in temperature. In
515, the DC level may also be trimmed though a buffer, such as
buffer 470 of FIG. 4. In this manner, it may be ensured that the
V.sub.sense voltage is inside the previously measured ADC input
range. Finally, a fine digital trimming operation may be performed
in the digitizing unit, such as in digitizing unit 462 in FIG. 4,
in 520.
Referring now to FIG. 6, an example operation of the temperature
sensor example block diagram 400 of a radar device of FIG. 4,
showing an IDLE state temperature measurement 600, is illustrated,
in accordance with examples of the invention. Like reference
numbers are used in the drawings to identify the same functional,
or functionally similar, elements. In this example, the temperature
measurements in an IDLE state use an SPI clock provided from or via
SPI 608, as no internal clock is available.
The selection of the temperature value is made through the
multiplexer 284 that outputs one temperature sensor value,
depending on the Temp_sensor_sel control signal 474, which in this
example is controlled by an SPI writing operation 610. If the user
of the radar device wants to measure the V.sub.sense analog
voltage, the switch 472 that routes the voltage on the SENSE pin
440 is closed. In this example, this operation is also performed by
an SPI writing operation 612 with an instruction to close the
switch 472. Also, in this example, in order to obtain the digital
value of the selected temperature sensor, it is possible to
activate or select an SPI read operation at 614. One of several
rising edges of the SPI read sequence may be used to initiate the
thermometric to binary conversion, the linearization via 614, the
storage of the digital value in a dedicated register via 616,
and/or sending the stored value to the user via 618.
Referring now to FIG. 7, an example of a timing diagram 700 in an
IDLE state temperature measurement is illustrated, in accordance
with examples of the invention, for example as may be performed in
the circuit of FIG. 6. Timing diagram 700 includes the timing of
the temperature sensor select (Temp_sensor_sel) signal 710, any
commands 720 from the SPI and the content of the register
Sensor_adc_reg 722. In an IDLE state, the register Sensor_adc_reg
722 is dedicated to store the digital value of the selected
temperature sensor. By default, temperature sensor 1 is selected
(with a binary code "01" (in Temp_sensor_sel signal 710) for the
multiplexer, such as multiplexer 284 from FIG. 6). In this example,
an SPI reading 722 of the Sensor_adc_reg 730 is performed: the
value (temp1_code 732) is stored and sent 734 to the user. Then the
temperature sensor 2 is selected 724 (with a binary code "10" (in
Temp_sensor_sel signal 710) for the multiplexer) and the value
(temp2_code 736) is stored. As an SPI command is composed of
several clock cycles, when the selection of temperature sensor 2
724 is applied, one of the clock cycles of the SPI also updates the
value in the Sensor_adc_reg 730. With another SPI command, the
temperature code of temperature sensor 2 is sent 738 to the user.
Subsequently, temperature sensor 3 is selected (with binary code
"11" (in Temp_sensor_sel signal 710) for the multiplexer) and the
value (temp3_code 740) is stored. It is sent 742 to the user with
another SPI command.
In examples of the invention, when the radar device is generating
or receiving an FMCW modulation, the temperature sensor system is
handled differently. The dynamic signals that control the
multiplexer 284 in the analog part of the chip (which perform
sensor polling) must be avoided. The use of polling avoids the
pollution of the modulation, generate some glitches, disturb FMCW
chirp linearity, which compromises the radar performances and
target detection. Referring now to FIG. 8, an example of a
functional state temperature measurement 800 is illustrated in
accordance with examples of the invention. Like reference numbers
are used in the drawings to identify the same functional, or
functionally similar, elements. In this example, an internal clock
in the digital part is available. Also, in this example, the
Temp_sensor_sel control signal 474 is periodically updated to
automatically change (poll between) the selected temperature sensor
422, 424, 426. In this example, sensor polling between the sensors
is performed using a (Temp_sensor_sel) control signal 810 initiated
by digital controller 262. In this example, all the digitizing
operations via. 814 and the storage of the digital value(s) via 816
are also automatically performed using this internal clock. The SPI
is still used to read the temperature: either to route the selected
temperature value(s) via switch 472 in response to control signal
812 the V.sub.sense voltage on the SENSE pin 440, or to read the
stored digital value and sending the stored value to the user via
path 818.
Referring now to FIG. 9, an example of a timing diagram 900 for
functional state temperature measurements is illustrated, in
accordance with examples of the invention. In these functional
states, a timer regulated by the, say 60 MHz, internal clock 905 is
started (noting that FIG. 9 is not to scale). The timing diagram
900 includes an indication of the content of temperature sensor
registers 920, 922 or 924, the application of temperature
thresholds 930, 932, 934 and the status of respective temperature
flags 940, 942, 944, as hereinbefore described.
In this example, every 10 .mu.s 912 a different temperature sensor
(T_SENS1 . . . T_SENS3) in this example is selected. The different
temperature sensor selection constitutes, in examples of the
invention, sensor polling. At the end of the 10 .mu.s timer period,
the digital value of the selected temperature sensor is stored into
a dedicated register. Temp1, Temp2 and Temp3 are the registers 920,
922 or 924 respectively corresponding to the digital values of
temperature sensor 1, 2 and 3. In examples of the invention, the
registers 920, 922 or 924 are periodically and automatically
updated.
The value in each register 920, 922 or 924 can be read 952, 954,
956 at any moment by using the appropriate SPI command 950. Thus,
the temperature code of any of temperature sensors 1 . . . 3 is
obtainable by reading the Temp1 . . . Temp3 registers, where the
value read may be sent to the user.
An over-temperature shutdown check may also be configured to run in
parallel with the temperature measurement. At the end of each 10
.mu.s timer, a check 931, 933, 935 is made to evaluate if the
stored digital value is above a programmable threshold 930, 932,
934 respectively, in an over-temperature process. The check
consists of comparing the value in, say, Temp1 register 920 to the
Temp1_threshold value 930 (and so on for Temp2 and Temp3). If the
value is below the threshold, the IC continues to work normally,
because this indicates that it is in a safe temperature operating
range. If the value stored is above the threshold, a flag, such as
Temp1_flag 940, Temp2_flag 942, or Temp3_flag 944, is generated. In
the example in FIG. 9, it is assumed that the temperature sensed by
temperature sensor 1 becomes locally higher in the chip, leading to
the generation of Temp1_flag 940. This flag indicates that a
shutdown must be commenced. In some examples, the threshold levels
may be programmable by the user using an SPI command 950. In some
examples, the threshold levels may be the same or different for
each temperature sensor and may be dynamically
changed/re-programmed at any time, if needed.
It is envisaged that tracking a temperature via a temperature
sensor and performing an over-temperature shutdown may be achieved
in a number of envisaged different ways, with different
implementations. In accordance with the examples illustrated in
FIGS. 4, 6 and 8, with the solution to perform a polling of all
sensors and taking into account a typical device state, IC area
available, accuracy required and covering all operational states
(IDLE, functional, etc.) and a sufficient number and variety of
sensors, provide the opportunity to use a single buffer 470 and a
single sense ADC 490. In this manner, an advantageous trade-off of
many operational factors may be achieved by use of the sensor
polling, in order to not pollute the FMCW ramp.
In the example topology of FIGS. 4, 6 and 8, the shutdown for each
temperature sensor 422, 424, 426 may be made at different
temperatures due to a use of a programmable threshold, which in
some examples is independently controlled for each temperature
sensor 422, 424, 426.
Referring now to FIG. 10, a simplified flowchart 1000 of an
over-temperature shutdown operation is illustrated, in accordance
with examples of the invention. As soon as the radar device is
operating in any functional state at 1002, a timer managed by the
digital unit starts at 1004. By default, in this example,
temperature sensor 1 is the one selected for the first functional
state. When a certain number N of clock cycles (e.g. N=600) is
reached, the value of the selected temperature sensor is stored
into the dedicated register at 1006, e.g. a first temperature for
temperature sensor 1, as in 1014. Then, the stored value
(Temp_code) is compared to the programmable threshold value (one
per temperature sensor) at 1008. If the comparison indicates there
is no over-temperature at 1008, it changes the selected temperature
sensor at 1010, e.g. transitions to temperature sensor 2 and starts
the cycle again at 1004. If there is an over-temperature condition
at 1008, the digital unit generates an over-temperature flag and a
shutdown operation is performed at 1012. At this point, a shutdown
may encompass one or more of the following, at 1016: powering down
of the receiver circuitry, powering down of the receiver circuitry,
entering a low-power mode of operation for the frequency
synthesizer(s), initiating a power management mode, etc.
Referring now to FIG. 11, an example timing diagram 1100
illustrates a timing of signals during a FMCW modulation phase, in
accordance with examples of the invention. The timing diagram 1100
includes an internal clock 1105. When the ramp_on signal 1114 goes
high, it signifies that the radar device enters into a modulation
phase 1116. The timer 1112 that regulates the selected temperature
sensor is ignored. The Temp_sensor_sel signal 1110 is `on hold` and
does not change for as long as the timer is `ignored`. Thus,
modulation occurs without any change of the temperature sensor
selected (i.e. there is no sensor polling). When the modulation
phase 1116 is finished, the ramp_on signal 1114 goes low and the
timer is effective again (i.e. sensor polling is initiated).
Without the modulation phase 1116, the way the values are stored
and the over-temperature checks are performed the same way as
described previously (FIG. 9 and FIG. 10). Thus, in this example
embodiment, it is proposed to switch to the FMCW modulation phase
1116 (e.g. with a transmission of chirps) during which sensor
polling is deactivated. In this example, sensor polling is
re-instated when the FMCW modulation phase 1116 is terminated (e.g.
In a silent mode with no modulation (or chirps)). In essence, it is
possible to make sure before sending the modulated signal (e.g.
ramp_on signal 1114 is activated) that the radar device is not in
an `un-safe` operational mode, so the radar device is checked to
ensure that no malfunctioning flag is activated.
For the sake of clarity, it is noted that the temperature tracking
and the over-temperature shutdown operations may be configured to
run simultaneously, in parallel.
The inventors recognized and appreciated that when the radar device
is in an IDLE state and no clock is available, a flash ADC with a
high number of bits may be used in order to share and process data
from multiple temperature sensors. The inventors recognized and
appreciated that, if the teaching of U.S. Pat. No. 8,970,234 B2 was
used in a FMCW modulated radar device, where a flash ADC could be
used for temperature sensors during an IDLE state when no clock is
available, glitches would be inherently generated that would
disturb the chirp linearity and corrupt the radar signal integrity.
Thus, examples of the present invention propose sharing of sensors
using a single buffer in a sensing unit and a single flash ADC when
supporting FMCW signals through a polling of the multiple sensors
at a particular sampling rate in order to read all of the
temperature sensed data. In this manner, with a use of a single
buffer and a single ADC a chip-area efficiency is achieved to
support several temperature sensors.
Furthermore, when an IDLE state is employed, and in order to avoid
the inherent glitches that would occur with switching (polling)
between multiple sensors, a single temperature sensor reading is
selected. Furthermore, in some examples, an accurate temperature
sensor system, using a single Flash-like ADC, is achieved by means
of an appropriate, and simplified, trim flow performed at different
block levels. Advantageously, examples of the invention also
support temperature reading measurements in both or either of the
analog domain and digital domain.
In the foregoing specification, the invention has been described
with reference to specific examples of embodiments of the
invention. It will, however, be evident that various modifications
and changes may be made therein without departing from the scope of
the invention as set forth in the appended claims and that the
claims are not limited to the specific examples described
above.
Furthermore, because the illustrated embodiments of the present
invention may for the most part, be implemented using electronic
components and circuits known to those skilled in the art, details
will not be explained in any greater extent than that considered
necessary as illustrated above, for the understanding and
appreciation of the underlying concepts of the present invention
and in order not to obfuscate or distract from the teachings of the
present invention.
The connections as discussed herein may be any type of connection
suitable to transfer signals from or to the respective nodes, units
or devices, for example via intermediate devices. Accordingly,
unless implied or stated otherwise, the connections may for example
be direct connections or indirect connections. The connections may
be illustrated or described in reference to being a single
connection, a plurality of connections, unidirectional connections,
or bidirectional connections. However, different embodiments may
vary the implementation of the connections. For example, separate
unidirectional connections may be used rather than bidirectional
connections and vice versa. Also, plurality of connections may be
replaced with a single connection that transfers multiple signals
serially or in a time multiplexed manner. Likewise, single
connections carrying multiple signals may be separated out into
various different connections carrying subsets of these signals.
Therefore, many options exist for transferring signals.
Those skilled in the art will recognize that the boundaries between
logic blocks are merely illustrative and that alternative
embodiments may merge logic blocks or circuit elements or impose an
alternate decomposition of functionality upon various logic blocks
or circuit elements. Thus, it is to be understood that the
architectures depicted herein are merely exemplary, and that in
fact many other architectures can be implemented that achieve the
same functionality.
Any arrangement of components to achieve the same functionality is
effectively `associated`, such that the desired functionality is
achieved. Hence, any two components herein combined to achieve a
particular functionality can be seen as being `associated with`
each other, such that the desired functionality is achieved,
irrespective of architectures or intermediary components. Likewise,
any two components so associated can also be viewed as being
`operably connected,` or `operably coupled,` to each other to
achieve the desired functionality. Furthermore, those skilled in
the art will recognize that boundaries between the above described
operations are merely illustrative. The multiple operations may be
executed at least partially overlapping in time. Moreover,
alternative example embodiments may include multiple instances of a
particular operation, and the order of operations may be altered in
various other embodiments.
Also for example, in one embodiment, the illustrated examples may
be implemented as circuitry located on a single integrated circuit
or within a same device. Alternatively, the examples may be
implemented as any number of separate integrated circuits or
separate devices interconnected with each other in a suitable
manner. Also for example, the examples, or portions thereof, may
implemented as soft or code representations of physical circuitry
or of logical representations convertible into physical circuitry,
such as in a hardware description language of any appropriate type.
Also, the invention is not limited to physical devices or units
implemented in non-programmable hardware but can also be applied in
wireless programmable devices or units able to perform the desired
device functions by operating in accordance with suitable program
code. However, other modifications, variations and alternatives are
also possible. The specifications and drawings are, accordingly, to
be regarded in an illustrative rather than in a restrictive
sense.
In the claims, any reference signs placed between parentheses shall
not be construed as limiting the claim. The word `comprising` does
not exclude the presence of other elements or steps then those
listed in a claim. Furthermore, the terms `a` or `an,` as used
herein, are defined as one, or more than one. Also, the use of
introductory phrases such as `at least one` and `one or more` in
the claims should not be construed to imply that the introduction
of another claim element by the indefinite articles `a` or `an`
limits any particular claim containing such introduced claim
element to inventions containing only one such element, even when
the same claim includes the introductory phrases `one or more` or
`at least one` and indefinite articles such as `a` or `an.` The
same holds true for the use of definite articles. Unless stated
otherwise, terms such as `first` and `second` are used to
arbitrarily distinguish between the elements such terms describe.
Thus, these terms are not necessarily intended to indicate temporal
or other prioritization of such elements. The mere fact that
certain measures are recited in mutually different claims does not
indicate that a combination of these measures cannot be used to
advantage.
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